Revenge on More than ex-Girlfriends
"The Dow Jones industrial average falls by over 500 points as the New York Stock Exchange responds to events over the weekend. (New York Times)" -Wikipedia
Events over the weekend
Unlike any other Webcomic writer of whom I know, the DM has never missed an update, even daily for several years. He always has them prepared and queued in advance. That means that unless he used the time travel that has been featured here and here lately, he could not have known exactly that it would be a weekend resulting in the biggest drop in seven years-and we all remember what happened seven years ago.